The Art of French Pastry

agents: cornstarch, cake
flour, and egg yolks. Using
only one of them would
not work, as cornstarch
would make the mix too
starchy, the cake flour
would make it too rubbery
due to the gluten, and if
you used more egg yolks
their flavor might
dominate. Using a
combination of the three
is the best of all worlds.